With each new war that occurs (the liberation of Kuwait, the action in Afghanistan and now in Iraq) you might expect the second world war to fade further into the mists of history. In fact, as the years go by, the quantity of material increases and the picture we have of it grows ever more detailed and vivid. A Writer at War is the diary of the Soviet engineer turned writer Vasily Grossman. It offers a wealth of new details and known facts seen from a new angle, but what is most striking about this book is the writer's extraordinarily subtle, almost childishly attentive view of the war.

Grossman is a very interesting character. He grew up in the Jewish town of Berdichev, in Ukraine, where in the first days of Nazi occupation his mother, having refused to be evacuated, was shot. Grossman, whose poor health made him unfit for military service, soon became one of three leading Soviet war correspondents. The works of the other two, Ilya Ehrenburg and Konstantin Simonov, became classics of Soviet literature. Grossman's works did not, and this book shows why.

The main task of the correspondent was to produce articles showing the heroism of the Soviet soldiers. The Red Star newspaper was practically the only source of information available to the soldiers and it was the hub of the Soviet propaganda machine, which had to maintain the soldiers' fighting spirit and their faith in the eventual Soviet victory over fascism. Grossman spent his time on the front line seeking out examples of heroism, but his notebook contains everything he saw and experienced there. Some of his notes were obviously made for himself; no censor would have let them through. However, even the articles about heroic deeds were "edited", if not rewritten, often turning Grossman's accounts of real events into biblical myths. In his letters home - included in the book - Grossman complained about this editorial meddling.

The battle of Stalingrad has a central place in the book, just as the battle was pivotal in the history of the war. Grossman's picture of it is quite different from the apocalypse traditionally described by military historians. The stories he tells, either overheard or told directly to him, are all carefully recorded, and sometimes completely untrue. Occasionally he admits as much in his notes, but, none the less, Grossman the writer is fascinated by all of them. If, having read this book, you read Grossman's most famous novel, Life and Fate, you will recognise a great many of the characters and events.

The story that particularly struck me was one about the dogs that lived among the ruins of Stalingrad, which could differentiate between the sound of a German plane and a Soviet one. The dogs started to bark long before the ground forces heard approaching German planes, but they were silent when Soviet planes flew over, as if they recognised their own. In the next paragraph Grossman describes how at night the Germans tied geese up around the outskirts of the villages they occupied, to be certain that the villagers did not get prior warning of any approaching trouble.

The detail with which Grossman describes the extermination camp of Treblinka horrifies by underlining the mechanical functionalism of those terrible death camps. Here the technical quality of Grossman's notes reflects his early career as a mining engineer. His article about Treblinka, published in Znamya, was used as evidence in the Nuremberg trials.

As Grossman moved west with the advancing forces, he became intent on calculating the number of holocaust victims. He attempted to include information specifically about Jewish victims in his articles, but the censor removed every mention of them. Although state Stalinist anti-semitism was not yet established, Soviet newspaper editors were already well aware of Stalin's personal opinion on the matter: "We should not categorise the dead according to nationality or race; they are all victims of fascism."

On the advice of Ehrenburg, Grossman became a member of the Jewish Anti-fascist Committee. He helped in the preparation of The Black Book, which detailed fascist crimes against the Jews.But after the war, the publication of the The Black Book was banned by the Soviet censor.

The repression of the committee did not daunt Ehrenburg or Grossman, but the latter paid dearly for his objectivity and his humane attitude to what he had seen. Life and Fate is one of the most honest books about the second world war. As soon as Grossman tried to publish it, KGB officers raided his apartment and confiscated every copy they could find. One copy, which Grossman had given to a friend for safe-keeping, survived, and eventually, after the author's death, a microfilm copy was smuggled out of the USSR. To this day Grossman's war diary has not been published in Russia. British readers are fortunate to have access to this honest and moving testimony.

· Andrey Kurkov's A Matter of Life and Death is published by Harvill. To order A Writer at War for £18 with free UK p&p call Guardian book service on 0870 836 0875.